Process for separating hydrocarbon

ABSTRACT

A process for the selective separation of constituents contained in a liquid hydrocarbon and chloro substituted hydrocarbon mixture, said constituents being paraffins, isoparaffins, naphthenes, olefinic hydrocarbons, aromatics and chlorinated aromatic compounds by selectively removing one of the constituents through forming nitrated compounds by reacting with NO.

United States Patent [1 1 Moser Nov. 12, 1974 PROCESS FOR SEPARATINGHYDROCARBON [75] Inventor: William R. Moser, Westfield, NJ.

[73] Assignee: Exxon Research Engineering Company, Linden, NJ.

[22] Filed: Dec. 27, 1972 [21] Appl. No.: 318,876

2,656,395 l0/l953 Benson 4. 260/688 3,366,686 l/l968 Rosenthal et al.260/688 3,658,922 4/1972 Drake 260/688 Primary Examiner-Herbert LevineAttorney, Agent, or Firm]ohn Paul Corcoran; Robert J. Baran [57] iABSTRACT A process for the selective separation of constituentscontained in a liquid hydrocarbon and chloro substi' tuted hydrocarbonmixture, said constituents being paraffins, isoparaffins, naphthenes,olefinic hydrocarbons, aromatics and chlorinated aromatic compounds byselectively removing one of the constituents through forming nitratedcompounds by reacting with NO.

5 Claims, N0 Drawings PROCESS FOR SEPARATING HYDROCARBON This inventionrelates to a process for either the separation or upgrading of varioushydrocarbon streams. In one aspect, this invention relates to the use ofnitric oxide for selectively removing various components contained inhydrocarbon mixtures.

In a copending application bearing Ser. No. 318,875 filed Dec. 27, 1972in the name of W. R. Moser, a process is described and claimed for theliquid phase reduction of nitric oxide with a hydrocarbon under mildnoncatalytic conditions.

The reaction and selectivities of N N0 and N 0 with hydrocarbons havebeen described in the prior art. For example, A. V. Topchiev, Nitrationof Hydrocarbons and Other Organic Compounds, Pergamon Press, New York,1959, pp. 226-268. W. H. Baum, J. G. Crist and E. V Nagel, U.S. Pat. No.3,428,414 Appl. June 2, 1966; M. Schienbaum, J. Org. Chem., 35, 2785(1970).

However, the reaction of nitric oxide with liquid phase hydrocarbons inthe absence of oxidants, catalysts, photo-induction, or other initiatingmolecules in unknown to those skilled in the art. Furthermore, itsselectivity towards reaction with various hydrocarbons is also unknown.

Briefly, the subject invention relates to a process for the selectiveseparation of constituents contained in a liquid hydrocarbon andchlorosubstituted hydrocarbon mixture, said consitituents beingparaffins, isoparaffins, naphthenes, olefinic hydrocarbons, aromatic andchlorosubstituted aromatic compounds, said process comprising the stepsof 1. Continuously contacting said liquid mixture with NO at atemperature and pressure sufficient to cause a reaction with at leastone of said constitutents contained in said mixture to form a nitratedcompound;

2. Isolating the nitrated compound resulting in Step 1 and leavingbehind an effluent;

3. Successively repeating Steps 1 and 2 until a. the nitrated compoundwhich results is that of the particular constituent which has thehighest order of reacting with said NO, or b. the effluent comprisessubstantially a single, unreacted constituent and recovering the saidparticular constituent by removal from the nitrated compound from Step3(a) by standard procedures, e.g., flash distillation. This separationsprocess has special advantage since the combustion stack gases fromrefineries, factories, plants, etc. provide local, cheap sources ofnitric oxide.

It has been discovered that pure NO or its admixture with inert gasesreacts with hydrocarbons in the following order of decreasingreactivity: olefinic saturated alkyl aromatics unsubstituted aromatichydrocarbons. The unexpected observation that saturated hydrocarbonsreact faster than aromatics is of special significance. This inventionhas the further advantage that the reaction of nitric oxide withsaturated hydrocarbons generally obeys the following order of groupreactivity with respect to carbon-hydrogen bonds:

Furthermore, alkylated aromatics reacted with nitric oxide according tothe following order: polyalkyl trialkyl dialkyl monoalkyl aromatic. Ithas further been observed that the positional isomers of alkylatedaromatics react in order of para ortho meta.

Illustrative hydrocarbons include the propanes, butanes, hexanes,heptanes, octanes, nonanes, undecanes, dodecanes and their higherhomologs; cyclopropanes, cyclobutanes, cyclopentanes, cyclohexanes,cycloheptanes, cyclooctanes, and their higher cyclic homologs; benzeneand its alkyl homologs, toluene, xylene, ethylbenzene, propylbenzene,tetralin, mesitylene, cumene, durene and the like; isomeric alkylatedhydrocarbons, para-xylene, meta-xylene, ortho-xylene, ethylbenzene;isomeric saturated alkanes, n-hexane, 2,3- dimethylbutane,2,2-dimethylbutane, 2- methylpentane, 3-methylpentane, n-octane, 2,2,4-trimethylpentane, 2,3,4-trimethylpentane, 2,4- dimethylhexane,3-methylheptane and the like; propene, butenes, pentenes, cyclohexenes,cycloheptenes, cyclooctenes and higher homologs and higher alkylatedhomologs; aromatic olefins, cisand trans-stilbene, sty rene and thelike.

The most preferred hydrocarbon compounds for reasons of availability andease of NO reduction are those alkylated aromatic hydrocarbonscontaining 7 to 25 carbon atoms.

Based upon considerable experimentation, it is possible to discloseworkable and preferred parameters in terms of volumes of the liquidhydrocarbons that are contacted per unit time with the gaseous NOcompounds and the ratio of the hydrocarbon to the NO concentration ofthe effluent in the various streams emanating from stationary sources aswell as mobile sources.

The reaction must be run in the presence of a liquid hydrocarbon such asthose enumerated hereinabove.

The reaction can be run in the presence of an inert gaseous diluent suchas nitrogen, neon, argon and the 0.04:1. Lower mole ratios give lowrates of reactionover the temperatures of 0 to 500C and are thereforeunsatisfactory. Higher ratios are generally more costly. Molar volumeratios of 10 to 0.5 volumes of hydrocarbon for each molar volume ofnitric oxide give good results and are hence preferred.

' Higher flow rates may accelerate the rate of reaction at a giventemperature since they may increase the quantity of NO brought intocontact with the hydrocarbon substrate.

However, flow rates of effluent gases between about 0.1 to 25 volumesper minute per volume of liquid bydrocarbon have been successfullyemployed while the best results have been obtained with flow rates perunit time from about 0.5 to 5 volumes per minute per volume ofhydrocarbon compound. The flow rate of gases used ordinarily depend uponthe quantity of hydrocarbon compound, the size of the reactor, thepressure and the rate of mixing of liquid and gas phases.

Utilizing reaction temperatures and reaction times as indicatedpreviously, good results have been obtained with reaction temperaturesranging between 0 and 500C. Lower temperatures give little or noreaction particularly with a more sluggishly reactive saturatedaliphatic while higher temperatures give rise to comployed, the moleratio of nitric oxide to the hydrocarbon compound, the nitric oxidepressure over the hydrocarbon, the flow rate, the mixing rate and thereaction temperature. Ordinarily the reaction produces molecularnitrogen and organic nitro compounds immediately but can require as longas several days when the more recalcitrant paraffins are the substrates.

In order to describe the workings of the invention, the inventiveprocess is described in the following illustrative examples.

EXAMPLE 1 The hydrocarbons (0.15 mole) in Table l were, excepting thesolid compounds, passed through alumina and degassed by the freeze-thawmethod. They were then placed in a glass autoclave and degassed again at165C by argon pressurization-depressurization cycles. Nitric oxide waspressurized into the reactor several times to 80 psi; finally thehydrocarbon was then saturated with nitric oxide at a pressure near 80psi. Then the pressure was adjusted to 80 psi and the rate of decreaseof nitric oxide pressure was recorded. The rate data were computeranalyzed by a standard linear regression analysis which was designed tocorrect observed pressures for the concomitant formation of molecularnitrogen. Table 1 shows the rate constants for the experimentallyobserved second order dependence of nitric oxide consumption from thegas phase for each hydrocarbon at 165C and 80 psi initial nitric oxidepressure.

The lowest reacting compounds were found to slowly react at 400 psinitric oxide pressure and 168C.

This example demonstrates that nitric oxide reacts with (a) olefins inpreference to other hydrocarbons, (b) longer chain paraffins inpreference to short chain paraffms, (c) trialkyl dialkyl monoalkylaromatics unsubstituted aromatics 5 haloaromatics, (d) saturatedhydrocarbons at equal or greater rates than its reaction with alkylaromatics or aromatics, (e) positional isomers of alkylated aromatics atdifferent rates.

EXAMPLE 2 A typical C -isomerate stream consisting of 0.66 g of2,2-dimethylbutane, 0.23 g of 2,3-dimethylbutane, 0.67 g of2-methylpentane, 0.37 g of 3-methylpentane, and 0.26 g of n-hexane wasdegassed and heated with nitric oxide at 168C at an initial pressure of400 psi. Gas chromatographic analysis of the final mixture showed that59.3 percent of the starting hydrocarbons has been consumed. Therelative uncorrected molar reactivity ratios for the individualhydrocarbons were determined as follows: 2,2-dimethylbutane (1.00),nhexane (1.52), 2-methylpentane (2.63), 3- methylpentane (2.69), and2,3-dimethylbutane (4.26).

A similar competition reaction utilizing equimolar isomeric octanes at168C and psi nitric oxide pressure after 28 percent conversion showedthe following relative order of molar reactivity: 2,2,4-trimethylpentane (1.00), n-octane (1.52), 3- methylheptane (2.58), and2,3,4-trimethylpentane (3.51).

Extensive competition experimentation utilizing equimolar concentrationsof aromatics and saturated hydrocarbons at 168C and 100-300 psi nitricoxide pressure, afforded the following order of reactivity. lsopropylbenzene was the reference compound and assigned a value of 100.

(Atm.)

Pressure standardized at 25C.

-Cont1nued Relative Compound Reactivity n-octane 6.0 n-heptane 4.5toluene 4.3 n-hexane 3.9 2,2,4-trimethylpentane 3.8 2,2-dimethylbutanel.2 benzene 0.00l

The order of group reactivities calculated from the above competitiondata is as follows. The reacting hydrogen atom is underlined.

Ar-CEI-(alkh This example demonstrates the feasibility of using nitricoxide to selectively remove hydrocarbons from isomeric mixtures, and thegeneral order of carbonhydrogen bond reactivity is defined i.e.,tertiary C-l-l secondary CH primary C-H.

EXAMPLE 3 A synthetic blend of fuel containing n-hexane, nheptane,benzene and toluene having a Research Octane Number (RON) of 59 wasallowed to react with nitric oxide at 110 psi initial pressure at 165C.After 30 percent conversion, analysis of the hydrocarbon fraction showeda composition equivalent to a RON of 75. v 5 This example demonstratesthat basic fuel stocks may be upgraded by this process by selectivelyremoving the low octane components from the mixture. This process hasthe further advantage that it may be carried out at a refinery utilizingnitric oxide which is generated in its combustion furnaces. What isclaimed is: 1. A process for the selective separation of constituentscontained in a non-olefinic liquid hydrocarbon mixture, saidconstituents being selected from the group consisting of normalparaffins, isoparaffins, naphthenes, and aromatic compounds, said methodcomprising the steps of:

l. contacting said liquid mixture with a purified stream containing onlyNO at a temperature and pressure sufficient to cause a reaction betweenthe NO and at least one of said constituents contained in said mixtureto form a nitrated compound; 2. isolating the nitrated compoundresulting in Step 1 and leaving behind an effluent; 3. successivelyrepeating Steps 1 and 2 until a. the nitrated product which results isthat of the constituent in said effluent which has the highest order ofreacting with said NO and whose parent hydrocarbon can be recovered bycatalytic hydrogenation, or

b. the effluent comprises substantially a single, un-

complexed consitiuent and recovering the said particular constituent byflash distillation from the product from Step 3(a).

2. A process according to claim 1 wherein the liquid hydrocarbon is oneconsisting of cyclooctene, cisstilbene, undecane, hexadecane,tetradecane, octane, heptane, cyclooctane, n-octane, 2,2,4-trimethylpentane, toluene, p-xylene, mesitylene, toluene, ethyl benzene,isopropyl benzene, t-butyl benzene, p-xylene, oxylene, m-xylene,tetralin, diphenyl methane, triphenyl methane, benzene, and Tia JuanaResiduum.

3. A process according to claim 1 wherein the liquid hydrocarbon is oneconsisting of isopropyl benzene, ethylbenzene, cyclooctane, mesitylene,cycloheptane, para-xylene, methylcylopentane, 2,3-dimethylbutane,2,3,4-trimethylpentane, ortho-xylene, n-hexadecane, n-tetradecane,3-methylheptane, ortho-xylene, 2,4- dimethylhexane, 3-methylpentane,n-undecane, ndecane, cyclohexane, cyclopentane, n-octane, nheptane,toluene, n-hexane, 2,2,4-trimethylpentane, 2,2-dimethylbutane andbenzene.

4. A process according to claim 1 wherein an octane number of a basicfuel stock is upgraded.

5. A process according to claim 1 wherein the temperature ranges from100 to 225C and the pressure-of the nitric oxide ranges from 100 to 300psi.

1. A PROCESS FOR THE SELECTIVE SEPARATION OF CONSTITUENTS CONTAINED IN ANON-OLEFINIC LIQUID HYDROCARBON MIXTURE, SAID CONSTITUENTS BEINGSELECTED FROM THE GROUP CONSISTING OF NORMAL PARAFFINS, ISOPARAFFINS,NAPHTHENES, AND AROMATIC COMPOUNDS, SAID METHOD COMPRISING THE STEPSOF:
 1. CONTACTING SAID LIQUID MIXTURE WITH A PURIFIED STREAM CONTAININGONLY NO AT A TEMPERATURE AND PRESSURE SUFFICIENT TO CAUSE A REACTIONBETWEEN THE NO AND AT LEAST ONE OF SAID CONSTITUENTS CONTAINED IN SAIDMIXTURE TO FORM A NITRATED COMPOUND;
 2. ISOLATING THE NITRATED COMPOUNDRESULTING IN STEP 1 AND LEAVING BEHIND AN EFFLUENT;
 2. A processaccording to claim 1 wherein the liquid hydrocarbon is one consisting ofcyclooctene, cis-stilbene, undecane, hexadecane, tetradecane, octane,heptane, cyclooctane, n-octane, 2,2,4-trimethyl pentane, toluene,p-xylene, mesitylene, toluene, ethyl benzene, isopropyl benzene, t-butylbenzene, p-xylene, o-xylene, m-xylene, tetralin, diphenyl methane,triphenyl methane, benzene, and Tia Juana Residuum.
 2. isolating thenitrated compound resulting in Step 1 and leaving behind an effluent; 3.SUCCESSIVELY REPEATING STEPS 1 AND 2 UNTIL A. THE NITRATED COMPOUNDRESULTING IN STEP 1 AND UENT IN SAID EFFLUENT WHICH RESULTS IS THAT OFTHE CONSTITREACTING WITH SAID NO AND WHOSE PARENT HYDROCARBON CAN BERECOVERED BY CATALYST HYDROGENATION, OR B. THE EFFLUENT COMPRISESSUBSTANTIALLY A SINGLE, UNCOMPLEXED CONSITIUENT AND RECOVERING THE SAIDPARTICULAR CONSTITUENT BY FLASH DISTILLATION FROM THE PRODUCT FROM STEP3(A).
 3. successively repeating Steps 1 and 2 until a. the nitratedproduct which results is that of the constituent in said effluent whichhas the highest order of reacting with said NO and whose parenthydrocarbon can be recovered by catalytic hydrogenation, or b. theeffluent comprises substantially a single, uncomplexed consitiuent andrecovering the said particular constituent by flash distillation fromthe product from Step 3(a).
 3. A process according to claim 1 whereinthe liquid hydrocarbon is one consisting of isopropyl benzene,ethylbenZene, cyclooctane, mesitylene, cycloheptane, para-xylene,methylcylopentane, 2,3-dimethylbutane, 2,3,4-trimethylpentane,ortho-xylene, n-hexadecane, n-tetradecane, 3-methylheptane,ortho-xylene, 2,4-dimethylhexane, 3-methylpentane, n-undecane, n-decane,cyclohexane, cyclopentane, n-octane, n-heptane, toluene, n-hexane,2,2,4-trimethylpentane, 2,2-dimethylbutane and benzene.
 4. A processaccording to claim 1 wherein an octane number of a basic fuel stock isupgraded.
 5. A process according to claim 1 wherein the temperatureranges from 100* to 225*C and the pressure of the nitric oxide rangesfrom 100 to 300 psi.